function y=FUN(x1,x2,x3,x4,x5,x6,x7)
   y1=174.42*(x1./x5).*(x3./(x2-x1)).^0.85;
   y2=(1-0.36*(x4./x2).^(-0.56)).^(1.5) ;
   y3=(1-2.62*y2.*(x4./x2).^1.16)./(x6.*x7);
   y=y1.*sqrt(y3);